FIG 7.

T. cruzi is detectable at very low levels in the chronic phase of infection, mainly in organs where systemic necrotizing vasculitis lesions are found. Mice were euthanized at 7 to 12 months p.i. after developing atrophy and/or partial or total paralysis of the posterior limbs. (A) Quantification by real-time PCR of T. cruzi DNA in the indicated organs 10 months after infection (green bars). The negative control was a quadriceps muscle taken from an uninfected mouse 10 months after infection of age-matched infected mice, shown at the right (uninf QM), and the positive control was a heart analyzed 30 days after infection (red). Data are shown for 3 mice for each tissue and condition, except for the acutely infected heart (n = 1). Rare parasite nests were visualized in all tissues whose names are circumscribed in orange. (B) Amastigote nest in a skeletal muscle myocyte adjacent to vasculitis. By H&E staining, a single parasite nest was found in skeletal muscles from a total of 12 mice analyzed. A, arteriole; M, skeletal muscle myocyte; Tc, T. cruzi amastigote nest. Magnification, ×200.